322 S. WELLER FAUNA OF THE FERN GLEN FORMATION 



eastern Missouri, which was being deposited in an entirely separate basin. 

 The so-called Chouteau of northeastern Missouri and Iowa is not the 

 typical Chouteau, and is to be correlated with the highest beds of the 

 Chouteau in central Missouri only. In following the Chouteau lime- 

 stone into southwestern Missouri it is found to occur with its typical 

 lithologic and faunal characters, but much reduced in thickness, near 

 the base of the Kinderhook, and not at the summit, as it is usually repre- 

 sented in geologic sections of that region. 8 In the Mississippi Eiver sec- 

 tion the same limestone, similar and sometimes identical in its litho- 

 logical characters with the formation at its most typical exposures at 

 Chouteau springs, Missouri, occurs at many localities in Missouri and 

 Illinois. A large fauna has been collected from the formation in Cal- 

 houn county, Illinois, which is identical in every respect with the fauna 

 at Chouteau springs. In the sections where the Fern Glen has its 

 typical development the limestone immediately beneath the red beds is 

 the Chouteau, although in none of these localities has it afforded a char- 

 acteristic fauna or in fact any fauna at all representative. 



A discussion of neither the entire fauna of the Chouteau limestone 

 nor any considerable part of it has ever been brought together in one 

 place, and many species in the fauna are as yet undescribed. Further- 

 more, all of the species of the Chouteau of central Missouri should not 

 be considered as constituting a unit fauna, but the zonal distribution of 

 the species should be investigated. Under these circumstances, there- 

 fore, it is impracticable to make a detailed comparison of the Fern Glen 

 with the Chouteau fauna. However, the most characteristic and typical 

 Chouteau species, such as Spirifer peculiaris, Pugnax missouriensis , 

 Reticularia cooper ensis, Productella cooperensis, Promacrus nasutus, 

 Triboloceras digonum, and Scliizoblastus rocmeri, do not occur in the 

 Fern Glen fauna, nor do they have any close relatives. Among the pre- 

 viously described brachiopods in the Fern Glen, excluding Spirifer ver- 

 nonensis and Cliothyris prouti, which were originally described from this 

 formation, all except one, Cliothyris incrassata, do occur in the upper- 

 most, non-typical beds of the Chouteau of central Missouri, in the Pier- 

 son limestone, which is the equivalent of these beds in southwestern 

 Missouri, and in bed number 7 of the Burlington, Iowa, section, which 

 is immediately subjacent to the Burlington limestone. Several of the 

 more conspicuous brachiopods of the fauna also pass over into the Bur- 

 lington limestone, and some of these are among the most abundant 



8 This Upper Kinderhook formation In Green county, Missouri, and elsewhere in the 

 southwestern portion of the state, has been called the Pierson limestone by the writer 

 in Journal of Geology, vol. 9, p. 144. 



